Huh? Carbon Dioxide Emissions Raise Risk of Satellite Collisions

In February 2009, two space satellites orbiting at speeds of almost 17,000 mph collided at a height of 482 miles over Siberia.

One was an operational U.S. communications satellite, Iridium-33. The other was a heavier, obsolete Russian military satellite called Cosmos-2251. For space scientists, the collision was a rude awakening to a worrisome kind of new math.

The ultra-high-speed collision turned two space orbiters in a cloud of debris with 2,300 objects. That made other scientists—climate scientists—take note, because changes in the upper atmosphere stand to increase the risk of space collisions. There are currently 21,000 pieces of trackable space debris, ranging in size from upper stages of old rockets to dime-sized chunks of metal.